/*
 * Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
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 *
 */

package com.sun.naming.internal;

import java.io.InputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.StringTokenizer;
import java.util.Vector;

import javax.naming.NamingEnumeration;

/**
 * VersionHelper was used by JNDI to accommodate differences between
 * JDK 1.1.x and the Java 2 platform. As this is no longer necessary
 * since JNDI's inclusion in the platform, this class currently
 * serves as a set of utilities for performing system-level things,
 * such as class-loading and reading system properties.
 *
 * @author Rosanna Lee
 * @author Scott Seligman
 */

public abstract class VersionHelper {

  private static VersionHelper helper = null;

  final static String[] PROPS = new String[]{
      javax.naming.Context.INITIAL_CONTEXT_FACTORY,
      javax.naming.Context.OBJECT_FACTORIES,
      javax.naming.Context.URL_PKG_PREFIXES,
      javax.naming.Context.STATE_FACTORIES,
      javax.naming.Context.PROVIDER_URL,
      javax.naming.Context.DNS_URL,
      // The following shouldn't create a runtime dependence on ldap package.
      javax.naming.ldap.LdapContext.CONTROL_FACTORIES
  };

  public final static int INITIAL_CONTEXT_FACTORY = 0;
  public final static int OBJECT_FACTORIES = 1;
  public final static int URL_PKG_PREFIXES = 2;
  public final static int STATE_FACTORIES = 3;
  public final static int PROVIDER_URL = 4;
  public final static int DNS_URL = 5;
  public final static int CONTROL_FACTORIES = 6;

  VersionHelper() {
  } // Disallow anyone from creating one of these.

  static {
    helper = new VersionHelper12();
  }

  public static VersionHelper getVersionHelper() {
    return helper;
  }

  public abstract Class<?> loadClass(String className)
      throws ClassNotFoundException;

  abstract Class<?> loadClass(String className, ClassLoader cl)
      throws ClassNotFoundException;

  public abstract Class<?> loadClass(String className, String codebase)
      throws ClassNotFoundException, MalformedURLException;

  /*
   * Returns a JNDI property from the system properties.  Returns
   * null if the property is not set, or if there is no permission
   * to read it.
   */
  abstract String getJndiProperty(int i);

  /*
   * Reads each property in PROPS from the system properties, and
   * returns their values -- in order -- in an array.  For each
   * unset property, the corresponding array element is set to null.
   * Returns null if there is no permission to call System.getProperties().
   */
  abstract String[] getJndiProperties();

  /*
   * Returns the resource of a given name associated with a particular
   * class (never null), or null if none can be found.
   */
  abstract InputStream getResourceAsStream(Class<?> c, String name);

  /*
   * Returns an input stream for a file in <java.home>/lib,
   * or null if it cannot be located or opened.
   *
   * @param filename  The file name, sans directory.
   */
  abstract InputStream getJavaHomeLibStream(String filename);

  /*
   * Returns an enumeration (never null) of InputStreams of the
   * resources of a given name associated with a particular class
   * loader.  Null represents the bootstrap class loader in some
   * Java implementations.
   */
  abstract NamingEnumeration<InputStream> getResources(
      ClassLoader cl, String name)
      throws IOException;

  /*
   * Returns the context class loader associated with the current thread.
   * Null indicates the bootstrap class loader in some Java implementations.
   *
   * @throws SecurityException if the class loader is not accessible.
   */
  abstract ClassLoader getContextClassLoader();

  static protected URL[] getUrlArray(String codebase)
      throws MalformedURLException {
    // Parse codebase into separate URLs
    StringTokenizer parser = new StringTokenizer(codebase);
    Vector<String> vec = new Vector<>(10);
    while (parser.hasMoreTokens()) {
      vec.addElement(parser.nextToken());
    }
    String[] url = new String[vec.size()];
    for (int i = 0; i < url.length; i++) {
      url[i] = vec.elementAt(i);
    }

    URL[] urlArray = new URL[url.length];
    for (int i = 0; i < urlArray.length; i++) {
      urlArray[i] = new URL(url[i]);
    }
    return urlArray;
  }
}
